The objectives of this research proposal are to examine the mechanisms for the plasticity of ocular dominance columns in the visual cortex of the cat and monkey, by 1) determining the relationship between the time course of normal development of the columnar system and the period during which plastic changes in the columnar system may be produced by monocular visual deprivation, 2) testing experimentally hypotheses which attempt to explain the observed changes in terms of simple neuronal interactions and 3) seeking evidence for changes in the synthesis or transport of molecules which may be involved in controlling these changes. Methods will be chosen which will permit the findings to be related to the known anatomical organization of the visual pathway. These include autoradiographic tracing of neural pathways in normal and visually deprived animals at the light- and electron-microscopic level, microelectrode recording with subsequent histological reconstruction of electrode tracks, and autoradiography of neuronal protein and RNA metabolism in deprivation.